When the police arrived with a search warrant at the Tattered Cover bookstore in Denver last spring, they wanted to know what books a particular customer had bought. The man was suspected of manufacturing illegal drugs, and two drug "cookbooks" had been found in his laboratory. A mailing envelope with the bookstore's return address and an identifying order number were found in a trash can outside.

From a law enforcement point of view, it was a routine matter, an attempt to tie a suspect to a crime. But for Joyce Meskis, the store owner, it was an assault on the First Amendment and the right to privacy. She refused the warrant and got a lawyer.

"This case is about the First Amendment. A bookstore is not like a hardware store with respect to criminal investigations," Meskis said.

Since then, her defiance has become a rallying cause among both First Amendment and privacy advocates.

"From a First Amendment perspective, having the government be able to go in and review an individual's buying or reading patterns will have an incredible chilling effect on a person's ability to consume," said Alvin Mark Domnitz, the chief executive of the American Booksellers Association.

In October, a trial court judge ruled that the Tattered Cover did not have to relinquish a month's worth of records, but did have to turn over records relating to the purchase of the drug cookbooks. Meskis has appealed.

In the past year, searches or subpoenas have also been sought for Borders bookstores in both Massachusetts and Kansas. The Kansas case also involves drug suspects; the Massachusetts case is a civil lawsuit and few details have emerged.

Informally, law enforcement officials have also sought information about book, music and video purchases made by customers of Amazon.com, according to the online retailer's lawyer, David Zapolsky. "We typically inform law enforcement that the request has the potential to violate privacy and First Amendment rights," Zapolsky said. "We don't give them the information.

"Where it gets tough is when somebody uses the actual product in the course of committing a crime. If somebody bought a crowbar from our hardware store." In those cases, Zapolsky said, Amazon tries to negotiate with law enforcement.

Prosecutors say they don't see a problem. "The issue is, is this evidence and is it clearly evidence?" said John Gill, a special counsel to the district attorney in Knoxville, who is on the board of the National Association of District Attorneys. "The more clear it is that you're going to find evidence of a criminal act, the more likely you are to be able to overcome people's privacy rights and seize that object or information. The more tenuous that connection to the crime, the less likely."

But Christopher Finan, president of the American Booksellers Foundation for Free Expression, said, "What we're afraid of is that it is a bad idea that is getting increasing publicity and occurring to more and more police -- to short- circuit the investigative process and go straight to a bookstore."

To many people it is not just a bad idea, it is one that feels fundamentally wrong. "There is something, almost a sanctity of the experience of the reader and the author that we understand," said Marc Rotenberg, director of the Electronic Privacy Information Center, a privacy rights organization in Washington.

The problem today, Rotenberg added, is that "between the word and the reader is this digital world." That means, whether in a bookstore, library or video store, that computerized records exist of which ideas a person has chosen to spend time with.

The first well-known attempt to investigate suspects' reading habits, or to use book purchases as evidence in court came during the Monica Lewinsky scandal, when the special prosecutor, Kenneth W. Starr, subpoenaed the records of two bookstores -- Kramerbooks in Washington, D.C., and the Georgetown outlet of Barnes & Noble -- to determine if Lewinsky had bought "Vox," a novel about phone sex by Nicholson Baker.

Until that subpoena, bookstores had basically been off-limits to prosecutors. Not so libraries and video stores. Libraries, according to Judith Krug, director of the Office for Intellectual Freedom of the American Library Association, were a focus of government investigators during the anti- Communist hysteria following World War II. In the 1980s, too, the FBI sought to enlist librarians in an effort to track the reading habits of suspected agents of the Soviet Union, particularly when it involved technical works.

"At this point almost every state has some protection for libraries," said Theresa Chmara, a Washington lawyer who works with the library association. "For bookstores," she noted, "there's no corollary."

Video stores have their own special statute. In 1988, after a Washington journalist uncovered what videos had been rented by Judge Robert H. Bork, the unsuccessful nominee for the Supreme Court, Congress passed a video privacy protection bill,

That legislation offered no protection in 1997, however, when police officers arrived at the Oklahoma City home of Michael Camfield, having learned from his local Blockbuster video store that he had rented the movie "The Tin Drum." The officers said it was illegal to possess the film, which won an Academy Award in 1979, because it was child pornography under Oklahoma state law.

"They broke a federal privacy statute to get my name and address," said Camfield, who won a $2,500 judgment against local officials, the minimum, for their violation of the federal Video Privacy Act. His claim against the city for violation of constitutional protections against search and seizure were rejected in the trial court.

A year after the Oklahoma battle came Starr's subpoena of Lewinsky's book- buying records. Though Judge Norma Holloway Johnson's decision that Starr's office had "shown a substantial relationship between the specific evidence sought and the grand jury's investigation" was made moot when Lewinsky agreed to cooperate with Starr's office, that ruling was still possibly the only one on the specific question of a bookstore's right to keep customer records private.

Jeffrey Rosen, an associate professor at George Washington University law school and the author of "The Unwanted Gaze: The Destruction of Privacy in America" (Random House, 2000), said, "There's been a dramatic shift in the law that happened so imperceptibly that we almost didn't realize how serious it was until the Lewinsky affair.

"For most of American history," he added, "it was considered unconstitutional and unreasonable to subpoena diaries, books" or other evidence that was not directly related to the commission of a crime.